Legionnaires' disease is a global public health issue. According to CDC's Morbidity and Mortality Weekly Report (August 2011), Legionnaires' disease increased 217% between 2000 and 2009. The disease-causing bacterium, Legionella pneumophila, is a waterborne pathogen found in natural and man-made water systems. Both potable and non-potable (utility) water supplies harbor Legionella pneumophila, and have been linked to outbreaks of both hospital- and community-acquired Legionnaires' disease.  

Ask The Experts

The following FAQs provide general and technical information about the disease. If you can't find the answer you're looking for, please click Ask the Experts tab and submit your question.


Persistence of positivity for the Legionella urinary antigen?

We had a patient test positive by urine antigen in January who is now testing positive again 4 months later. If recurrence is rare, is there a specific time period that the test will convert to negative following the disease? Does a persistently positive test imply that Legionella infection still persists? Or does it imply that it wasn’t completely eradicated from her system?

Prolonged urinary antigen excretion has been reported. Most of the patients that we have evaluated converted to urinary antigen negative between 30-60 days. Factors related to prolonged excretion have included severity of illness and immunosuppression.

This was recently reviewed – Sopena N, Sabria M, et al. Factors related to persistence of Legionella urinary antigen excretion in patients with Legionnaires’ disease. Eur. J. Clin. Microbiol. Infect. Dis. 2002. 21:845-848.

Which antibiotics are effective against Legionnaires’?

Is Meropenem effective in clearing Legionnaires’ disease? What is the chance of survival with lung cancer and continuous smoking?

Meropenem has some activity against Legionella, but would not be considered an effective antibiotic for Legionnaires’ disease. For survival of lung cancer, it would be best answered by the patient’s oncologist.

Follow-Up Question:

The doctor changed my mother from meropenem to gentamicin. Will this be effective in clearing the Legionella? I wonder why the doctor won’t put her on the Cipro which is supposed to be the most effective drug. She is on oral Zithromax.


Gentamicin is inactive against Legionella. Oral azithromycin is highly active against Legionella. If your mother is critically ill in the ICU, then printout this article ( from the Publications section, and show it to her physicians. If your mother is recovering nicely, then oral azithromycin is fine.

Is there an antibody test that can be used to diagnose pneumonia many months ago?

I had pneumonia (shown on chest x-ray, single-lobe/105°F fever) 5 months ago. Is there a test for the Legionnaires’ disease antibodies that can be taken at this point to prove or disprove that it was Legionnaires’ disease? I still feel tired and breathless most of the time. I have had diarrhea for quite a while now. My doctors don’t think it is an issue.

You can have a blood test for Legionella performed (Legionella serology for antibodies). If the test is positive, this is circumstantial evidence that the pneumonia was Legionnaires’ disease.

Your doctors may be right about the issue of Legionnaires’ disease. You have been treated successfully and you need no further antibiotics. In the FAQs, we provide information that many patients who contract Legionnaires’ disease will experience fatigue for more than a year, although almost all will recover. Diarrhea is common, but it should resolve when the pneumonia resolves, so consult your physician if it has not resolved. Clostridium difficile colitis is a syndrome caused by antibiotics and this diagnosis might be considered. We recommend that patients with Legionnaires’ disease quit smoking and continue to be active even if they feel fatigued.

Legionella is in the water supply of our hospital?

We have documented colonization with Legionella in the hospital water supply of our small hospital. We have not observed cases of Legionnaires’ disease at this time (but underdiagnosis is probable), and after a successful trial of superheat and flush, colonization recurred. It is technically impossible to resume that disinfection method (old distribution system). Thus, we cannot disinfect the water supply and we cannot shut down the hospital. Is it reasonable to withhold drinking water from our patients and to institute systematic laboratory testing for all patients with hospital acquired pneumonia in an attempt to treat with anti-Legionella antibiotics with minimal delay?

Yes, your approach is very reasonable. We would not recommend disinfection of your water supply since your patients are not high risk. We would recommend that your clinical microbiology lab adopt the urinary antigen test if the Legionella in your water supply is serogroup 1. Physicians should order it for patients who have contracted hospital-acquired pneumonia.

If your patients contract hospital-acquired pneumonia of uncertain etiology, we recommend adding a quinolone (e.g., levofloxacin) as part of empiric therapy.

Please download the Allegheny County Guidelines on the Guidelines page. These guidelines, which are simple and cost-effective, will protect your patients from Legionnaires’ disease. Your suggested approach is in concordance with the guidelines. Knowledge of colonization can eliminate mortality without tremendous expense by adopting laboratory testing and using effective antibiotics.

Thermal springs for a transplant patient?

What are your recommendations concerning thermal springs and hot baths for immunocompromised patients or transplant receipts.

The risk is low, but not zero. The patient should avoid breathing in vapors. Also, we recommend that transplant patients and highly immunosuppressed patients not drink tap water. Instead, boil water and cool it for drinking. When traveling or not at home, bottled water might be preferred.

Testing for Legionella many months later?

I am the patient/nurse who had Legionnaires’ disease and was waiting for results from a hot tub and shower. I had a positive urine antigen. The hot tub was culture positive but the showerhead was culture negative. We are still waiting to see if the culture yields L. pneumophila type 1. The person who stayed after me had Pontiac Fever according to the epidemiologist.

Question: If he had symptoms several weeks ago, are there any laboratory tests that may confirm this diagnosis? The epidemiologist thought it was too late to test him. 


The antibody serology (blood test) can remain positive for 3 – 6 months (or longer in some cases) after the infection.


Can Legionella cause endocarditis?

Can Legionella cause endocarditis? Are there documented cases that legionella bacteria have migrated to the heart causing vegetations on the heart valves and requiring valve replacement?

Yes, numerous cases of hospital-acquired legionella endocarditis have been described – the largest series is from Stanford University. The source was the drinking water of the hospital.

Legionella is transmitted to the heart in 2 ways: bacteremia from hospital-acquired pneumonia or possibly contiguous spread from the use of contaminated water post-cardiac surgery. If you have such a case, it may be reportable as a case report in the peer-review literature. The water supply of the hospital must be cultured for legionella, and ideally, the results of Legionella serology and urinary antigen should be available for the patient. Pericarditis has also been reported.

Legionella is in the water supply of our long term care facility

  1. Recently a resident of our long-term care facility was found to have Legionella pneumonia. Tests performed by the health department revealed that Legionella is in our water supply. Is Legionella often found in long-term care facilities?
  2. We have had 4 other cases of pneumonia in which urine antigen tests have been negative- however, two of these patients did not really improve clinically until they were put on Zithromax for their antibiotic therapy. I also raised the question of aspiration and was told this is not a problem, however you indicate that it is. Now, I am flushing the nasogastric tube of my patient with sterile water until we have treated our water supply
  3. He has already had documented aspiration pneumonia 2 times and is one of the patients that did not improve until Zithromax was given. If his urine antigen test was negative can we feel confident that he did not have Legionella?


  1. Yes. It is present in the drinking water of many long term care facilities. No formal survey has yet been performed – but 20-70% of hospitals harbor Legionella. In addition, numerous cases of Legionnaires’ disease have been reported from long-term care facilities and nursing homes (Fang GD, Med 90; Marrie TJ 86, Loeb M 99, Maesaki 92, Brennen C 87). We are now recommending that all such facilities culture their water supply ( Seenivasan M, Journal of American Geriatrics Society, 53:875-880, 2005).
  2. We agree with your approach. Aspiration has been shown to be a major mode of transmission for Legionnaires’ disease and studies in long-term care facilities show that aspiration occurring from nasogastric tubes, indeed, is a risk factor for aspiration (Loeb MJ 02, Am Geriatrics 99; Seenivasan M, in press).
  3. No. Although the sensitivity is about 85%-90% for Legionella pneumophila, serogroup 1, it will not detect other Legionella spp or serogroups. Azithromycin (Zithromax) is effective therapy. Levofloxacin (or another quinolone) might also be used empirically for nursing home pneumonia of uncertain etiology if the water supply harbors Legionella. Quinolones also cover other common pathogens in nursing home pneumonia including gram-negative rods.

Antimicrobial therapy for Legionnaires’ disease?

Is there any data that supports that one quinolone is more effective than another? A physician in our hospital thinks that gatifloxacin is superior, yet I don’t see it recommended as a primary regimen in The Sanford Guide to Antimicrobial Therapy 2003 edition.

In the textbook Antimicrobial Therapy and Vaccines and the companion website,, we explicitly caution against the use of gatifloxacin for Legionnaires’ disease. To our knowledge, there is not a single culture-confirmed case ever cured with gatifloxacin. We believe it should not have been FDA-approved without that clinical experience.

The most potent quinolone in the intracellular model is levofloxacin. The largest clinical experience by far is with levofloxacin with an extraordinarily high rate of cure (Yu Chest 2004). Ciprofloxacin has also been successfully used. Moxifloxacin and gemifloxacin may be equally effective, but clinical data is minimal


PCR positive and culture negative water samples?

This is a general question about lab tests for Legionella, but I thought you may be able to help me. I know that the Pittsburgh VA is an authority on Legionella. We recently tested water samples from a camp that hosts retreats for both children and adults, after a Legionellosis case in our region occurred and the patient claimed he had visited the camp a few days before developing symptoms, We sent the samples to our state’s public health laboratory and they all came back culture-negative but positive by PCR. The public laboratory sent the results to us saying that this test is still experimental, but they could not explain what that means in terms of control measures. I get the impression that PCR detects Legionella DNA, but only a positive culture can define if the Legionella is viable enough to infect a person. Is this correct? Are repeat tests recommended?


The director of this camp is very concerned that any of the lab results came back positive and is thinking about repeating testing. He has looked into this and found a lab that will charge upwards of $1000 for each investigation. Could you also tell me an estimate of the cost of sending samples to the Pittsburgh VA Lab?


You are correct that the meaning of a positive PCR/negative culture is unclear. It is for this reason that culture remains the “gold standard” for investigation of cases. We would expect that the cultures would be positive if a water reservoir at the camp was the source of exposure – unless a disinfection procedure had been applied.

An individual that is active enough to go to a camp also would have had the opportunity to be exposed to Legionella in locations besides the camp. The camp director has done all that is necessary and follow-up cultures are not indicated. If they want to culture anyway, our lab’s information can be found under the Legionella Testing tab.


Pneumonia in a traveler

I have a patient in my ER as we speak/type who I suspect of having a Legionella infection. She is a 62 yr old lady who returned two weeks ago from a month stay in Sri Lanka. She has a fever which started 2 days ago. She also developed hallucinations, diarrhea and a cough. Her CRP is 350 (N range<10). Her X-ray showed an upper right infiltrate. Because of her travel history and clinical signs I suspect a legionella infection. However her urine antigen test (Binax) is negative. What kind of serotype can be found on Sri Lanka? PubMed shows only 1 hit (Ceylon Med J 2000) where only 1 out of 16 Legionella isolates was tested and yielded serogroup 1.


We agree the history is suggestive of Legionnaires’ disease. The urinary antigen is sensitive only for serogroup 1 which is the predominant serogroup in Hong Kong and Taiwan, so I suspect that it is also the predominant serogroup in Thailand. (But I could be wrong.)  n Australia, Legionella longbeachae is quite common which would not be detectable with the urinary antigen test. There are species and serogroups of Legionella that are missed by the urinary antigen test as you indicate. The test is highly specific so that if it is positive, the patient has Legionnaires’ disease. Your microbiology lab should attempt to culture the sputum with selective Legionella media as described on Serology should be obtained today and later to confirm the diagnosis. A gram stain of sputum should be done. Legionella would present with numerous leukocytes, but no visible bacteria.

I would certainly cover this patient with an anti-legionella antibiotic such as azithromycin or levofloxacin. And then switch when a pathogen is definitively identified. Keep in mind Meliodosis if she has been in rural areas.

Legionella in the homes

I am a physician at the District Health Office. We have noticed an increase in the number of reported cases of Legionnaires’ disease. These have all been non-nosocomial, non-travel associated Legionnaires’ disease, with a number of patients barely
leaving their houses. It was decided to test the domestic and municipal water supplies for the presence of legionella. We also tested the water of premises where there had been no Legionnaires’ disease. Having found legionella, the correct course of action is not entirely clear. We have identified 3 possible scenarios and would be grateful if you could advise.


  1. Legionella found in the domestic water supply of a known Legionnaires’ disease patient.
  2. Legionella found in the domestic water supply of healthy individuals.
  3. Legionella found in the domestic water supply of those with lung disease of immunocompromised patients, in the absence of Legionnaires’ disease.


  1. Ideally, molecular subtyping of the patient isolate and the environmental isolate would support that the source of the Legionella is from the home. However, I know the legionella isolate from the patient often is not available especially if the diagnosis was made by the urinary antigen test. That said, the home could be disinfected because of the occurrence in the patient’s home. Certainly, the patient and the family would feel safer. Disinfection is also suprisingly easy in a residence. Superheat and flush can be used. The flush should be at least 30 minutes – see our website for details of the superheat and flush (Publications on disinfection by YSE Lin, 1998 ).
  2. No action. The reason is clearcut. Legionella can be found in the majority of buildings over 3 stories tall. Since it is a common colonizer of drinking water, all individuals are exposed on a regular basis to Legionella.
  3. No. See our Reply to Question #2. The logical site to perform culturing of drinking water would be a building in which high risk individuals congregate; in such a situation, environmental culturing would be cost-effective. That specific situation is a hospital and many countries now routinely culture their water supply. The results allow the hospital to make a rational decision on how to prevent a preventable infection. Such a policy has been implemented in Pittsburgh, state of Maryland, Spain, France, Denmark, Taiwan, Netherlands, Italy, and Germany. Two other points: Legionella is not contracted via showering. The major mode of transmission of legionella is not aerosolization, but aspiration. So cooling towers are overemphasized as sources of Legionnaires’ disease.

Urine for Legionella antigen test

What type of lab test should we do for a Legionnaires’ diagnosis? If we want to run the Legionella urine antigen by ELISA, can we use urine that has been stored for over 24 hours, or do we need to use fresh urine?


Refrigerate the urine if the test cannot be performed immediately. Test results will decline over time, but may remain positive for up to 3 weeks if the infecting Legionella is L. pneumophila, serogroup 1.

Legionella anisa is in our hospital water supply. Should we disinfect?

Legionella anisa was found in a surprising number of the distal water sites in our hospital. No cases of Legionnaires’ disease have ever been detected, although we do not have Legionella culture available as a diagnostic test. Since the urinary antigen does not identify L. anisa, should we disinfect our water supply?

The majority (>90%) of cases of Legionnaires’ disease reported in the  U.S. are caused by Legionella pneumophila. L. anisa is included in the “other species” group which is less than 10% for all other Legionella species. There are 48 named species of Legionella, with approximately half having been implicated in human disease.

L. anisa is frequently isolated from environmental specimens but very rarely causes disease.  Disease caused by other Legionella species, like L. anisa, occurs almost exclusively in immunocompromised individuals. Only a handful of cases attributed to L. anisa  have been reported. We consider this species as nonpathogenic (Yu, J Infect Chemother 2004, Stout, in press). And, we would NOT disinfect your water supply.


Can one be tested for Legionella after the pneumonia has been cured?

Can you test for Legionnaires’ disease after you have been treated and the pneumonia has subsided?

A blood test, antibody serology, can be performed. It is most accurate 4-12 weeks after the pneumonia. The ideal circumstance is to have a blood test obtained during the pneumonia (acute sera) followed by a repeat test 4-12 weeks later (convalescent sera). Another test is the urinary antigen test, but the accuracy of this test decreases 1 month after the pneumonia.

L. pneumophila serogroup 13 and drowning?

L. pneumophila serogroup 13 and drowning: A female aged 27 year old was admitted to intensive care unit with respiratory failure due to aspiration pneumonia after drowning in River Clyde in Glasgow, Scotland, UK. Culture of tracheal aspirate yielded growth of Legionella pneumophila serogroup 13. The patient seroconverted to Legionella pneumophila serogroup 13 before she died of respiratory failure.


My questions are:

  1. How significant is Legionella pneumophila serogroup 13 in a patient with aspiration pneumonia?
  2. Has this particular serogroup been associated with Legionnaires’ disease in patient who drowned in urban river water?
  3. Has been any documented case fatality reports of Legionella pneumophila serogroup 13 in the literature? If Yes, Please provide the references.

  1. Serogroup 13 is extremely unusual and we have never documented a culture-confirmed case. However, Mona Schousboe New Zealand and Chris Heath Australia have documented 1 case each of culture-confirmed serogroup 13 in community-acquired legionellosis. (Yu VL, et al J Infect Dis 2002; 186:127-128). In this international surveillance study of culture-confirmed community-acquired LD, 2/508 patients were infected by serogroup 13.
  2. No. There have been 2 cases of drowning associated with Legionnaires’ disease. A serogroup 10 in the Lancet 1988:2:460 and serogroup 3 Kansenshogaku Zasshi Dec 1995;69:1356-1364. This is further evidence of the importance of aspiration.
  3. Not to our knowledge. You have a reportable case! I will put you in touch with Christopher Health and Mona Schousboe and you should combine your experience into an important case report. I suggest you consider Emerging Infectious Disease as the journal for submission.
  4. Epilogue: Faris B, Faris C, Schousboe M, Heath CM. Legionellosis from L. pneumophila serogroup 13. Emerg Infect Dis 2005; 11:1407-1411.

Is endotoxin a virulence factor?

Why is endotoxin not a virulence factor for Legionella since it is a gram-negative bacterium?  I work in a biotech company and develop assays for endotoxin detection.  I am thinking of using endotoxin detection as a method for environmental monitoring (not for diagnosis).

No clinical evidence has suggested the possibility of endotoxin-mediated disease in humans. Endotoxin is not used for diagnosis and is not a virulence factor for Legionella A murine model showed that mortality was not related to endotoxin production (Pastoris MC, J Med Microbiol Aug 1997;46:647-655).


Quinolone duration for Legionella if myasthenia present?

I had spoken to you about a very sick patient with severe Legionella pneumonia. He had renal failure from severe rhabdomyolysis, intubated, and in septic shock. Thank you so much for your help. He finally walked out the hospital. I have a question about another severe Legionella pneumonia patient. This patient has cavitary Legionella pneumonia but has myasthenia gravis. I have him on Avelox and Zithro.


As you know the Avelox is already worsening his myasthenia. He was very sick with a big consolidation and abscess now extubated doing well only on Avelox and Zithro. I do not think I can give anything else. I am planning on giving him 6 weeks of above regimen while I watch closely for respiratory compromise. Do you have any ideas? Thank you so very much for your help.


Congratulations on your successful therapy for a patient with shock, rhabdomyolysis, and renal failure. These are all risk factors for high mortality, so your patient was fortunate that you were his physician.

With respect to 6 weeks of therapy with the quinolone in face of a history of myasthenia gravis: If this patient has no other immunosuppressive risk factor including corticosteroids, 6 weeks of antibiotic therapy is likely unnecessary. If his myasthenia gravis is worsening on therapy and his pneumonia is under control, the quinolone might be discontinued. Azithromyin has been used successfully as monotherapy for many patients, as you know. And, if combination therapy is used for severely-ill patients, the advantage of combination therapy will be in the first few days of therapy.

So, you have the option of discontinuing the moxifloxacin now and using azithromycin only. Total duration might be 14 days if he is afebrile and clinically improving. The chest radiograph gives an indication of severity of illness at onset, but radiographic resolution cannot be used as a prognostic sign.

Pediatric Legionella?

A colleague from another hospital called me to ask about 4 month old infant in their PICU with bilateral pneumonia and shock. A urine test was positive for Legionella. A culture and PCR of sputum were just taken. The boy had diarrhea before it all started. It is not nosocomial infection and his immune status is normal. He has leukopenia and high LDH but with normal LFT. He received azithromycin orally for 2 days and his condition is getting worse. I advised him to give IV azithromycin, and because of his severe condition, to add levofloxacin to the treatment (not sure if it is better than monotherapy). He will also take some tests for immune deficiency and we are waiting for final tests for the Legionella. I will be happy to hear your opinion about the treatment, and, of course, about the case. I feel that we should have a registry for pediatric Legionella

Don’t worry about using non-evidenced based approaches, just follow your instinct as to what is right and document it. After a while, the evidence will come and you will be the one who provided it. You can use rifampin for 2 – 3 days. Rifampin will interact with many other drugs but it is the most potent agent against Legionella in vitro and in vivo. 2 – 3 days may be pivotal during this critical stage, and a short duration may be enough. In the meantime, culture the drinking water of this infant! Use DGVP media to eradicate commensal water flora and save the Legionella that you isolate.

Evaluation for Sjogren’s syndrome and lymph node biopsy?

I have Hashimoto’s Disease but, besides the Legionella diagnosis (which don’t explain all my symptoms); I have no other explanations for my symptoms since November 2008. I have taken several antibiotics but it doxycycline heclate worked very well to clear up most of my symptoms.


I was diagnosed with Legionella this past week by Roswell Park Infectious Disease Department via a blood test by EIA. In addition to the Legionella diagnosis, the following flags have also been raised: Mycoplasma exposure, high Eisinophils, high sed. rate, etc. My symptoms over the months since November 2008 have been: 


  • (11/2008) Itchy scalp, rash on inner thighs, congestion, double ear infection, nose sores, red eyes, swollen lymph nodes behind ears
  • (12/2008) Scaly rash on face, excessive vaginal discharge, rectal rash, rash under breasts, excessive bleeding in mouth while/after brushing, swollen neck lymph nodes, angular cheilitis, rash on neck
  • (1/2009) Rashes in armpits, arm rashes, foot dryness, sores on back-arms-ears, scalp flaking, ear dryness, hand rash, lesions on finger tips, crusty and oozing belly button
  • (2/2009) Blood when voiding, cracks on ears, hand rash, genital and rectal rash with discharge and foul smell, lumps on vaginal labia, pelvic region sensitivity, itchy feet, angular cheilitis, slight scalp flakiness
  • (3/2009) Swollen lymph nodes in neck size of golf balls, severe coughing which results in vomiting phlegm-blood-food, diminished appetite, weight loss (20 lbs) (4/2009-7/2009). Severely dry eyes that stick, almost seal closed and more of the same as listed
  • (7/2009) Was put on Doxycycline Heclate and all symptoms improved – not totally gone but definite improvement
  • (8/2009) Stopped Doxycycline Heclate and vaginal and rectal rash and discharge returned to a lesser degree but still back, swollen lymph nodes in neck smaller but still there, had a pain in my left leg (now is gone), have a rash on face-back of neck/between breasts/back/armpits, itchy scalp, and belly button crusty and oozing


So, my questions are:
Do I have Legionella?
Should I pay to have my private residence water checked for Legionella pneumophila?

The information that you have provided is insufficient to definitively answer your question. Was a chest x-ray ever performed? What is the precise number for your sed. rate and eosinophilia?

The symptoms that you describe are consistent with Sjogren’s Syndrome which should be evaluated. This malady has been linked to Hashimoto’s. The larger lymph node might be biopsied to rule out other more serious diseases.

With respect to culturing your drinking water, this probably will be less useful in your specific case. Doxycycline is curative for Legionella (and Mycoplasma pneumoniae) and we have found that recurrent Legionnaires’ disease almost never occurs. The first attack apparently confers some immunity. The second reason is that the sources of drinking water are numerous, and your home may not be the source. Regardless, we could culture your drinking water, but I think you may be protected by your first episode. However, if you ever require steroid therapy in the future, the info about Legionella in your drinking water may be useful. The cost for the Legionella cultures is not high; we will perform it gratis in your unique case, but we do request that you pay for shipping charges.

Your next step: See a rheumatology specialist for evaluation of Sjogren’s disease. And ask for his/her opinion of a lymph node biopsy – if the lymph nodes have regressed back to normal size than it is ok not to biopsy. Please keep us posted, but your Legionnaire’s disease appears to have been cured.

Preventative therapy?

Can you treat a patient before they have symptoms to prevent Legionnaires’ disease if you know that they may have been exposed (water supply where they stayed tested positive)?

Many buildings have Legionella in the drinking water, and you have undoubtedly been exposed to Legionella in the past. Most patients who contract Legionnaires’ disease have a risk factor. Cigarette smoking is the most common. Disease in which the immune system is compromised is another. If you develop high fever and symptoms of pneumonia (cough), see a physician.


L. pneumophila serology?

I am about to see a young patient who has had a three months of upper respiratory symptoms without a fever. He was found to have the following L. pneumophila serological results: IgG-1: 128 (ref </=64), IgM-1: 512 (ref </= 256)


Others at his building have had similar symptoms. I only have info from a phone call and I have little additional information. The MD didn’t know if there was a fountain in the building lobby. I am suspicious regarding the diagnosis of Legionnaires’ in the “index case.” Any thoughts?


Surprisingly, this is not an uncommon problem, and we get this question occasionally. The missing info is whether he has ever had pneumonia in the past, especially within a year. It would also help to know the past medical history and the history of cigarette smoking.

Assuming that he has no overt history of pneumonia, this serology suggests that he has contracted Legionnaires’ disease and has either subclinical pneumonia or Legionella infection without pneumonia.  Assuming no other striking info comes from his PMH (including no antibiotic history); I would order a chest x-ray. It might be justifiable anyway given his prolonged duration of URI.

If it was negative, you have 2 pragmatic choices:

1) Give him empiric azithromycin 500 mg for 7 days

2) Have an ENT evaluate him for chronic sinusitis

(I had similar symptoms to this patient and didn’t use antibiotics for a likely viral URI. My cough exacerbated in the third month and I was moved to another room due to spastic coughing fits lying supine with copious rhinorrhea. I had a nasal endoscopy and laryngoscopy with the ENT rhinologist. [See CID article, Jan 2012] The endoscopic cultures revealed H influenza-beta-lactamase positive. I took Augmentin with clinical response in 3 days; I took my last dose of Augmentin last night and cough has disappeared.)

Based on the limited history, I would give empiric azithro. One reason is relief of anxiety for both referring physician and patient. (For the other employees with similar symptoms/anxiety about Legionnaires’ disease, I don’t believe that decorative fountains cause Legionnaires’ disease.)

When you get the remaining history, email me again. We have devised an inexpensive solution for buildings which are colonized with Legionella and are not healthcare facilities with high-risk patients. Example: hotels, dormitories, office buildings.

Pneumonia may be cured?

My husband is 31 and has a fever ranging from 38 °-40 ° C, severe pain, sore throat, chills, sweats, muscle aches, headaches, cramps, diarrhea, and nausea. It has been a hard two days at home. We gave him pills for his fever which were effective for 3 hours. He was hospitalized after 3 days and the symptoms persist for 3 more days. After 5 days the fever wasn’t controlled by pills or neo-melubrine. He was given an antibiotic for strep throat (clindamycin).


On the fifth day, we consulted infectious diseases, and he suggested it was Legionnaires’ disease. We performed blood studies and the lymphocytes were 8 with the reference range of 20 – 40. The doctor changed to oral antibiotics (Klaricid OD klaritromicin 500 mg) taken every 12 hrs for 10 days and Avelox – Moxifloxacin 400 mg tablets for 5 days. These antibiotics cured all the symptoms. The doctor said the tests to determine if it was Legionnaires’ are done in the U.S. and the results will take 15 days. For this reason, these antibiotics were prescribed because we couldn’t wait on results. No tests were done to determine if it was Legionnaires’.


 My question is: How to know if my husband has the Legionella bacteria after receiving this treatment? He was released and began to work, but he went to the doctor and there are still spots in the lungs. I am very upset because I hope he does not have a relapse. 

Klaritromicin and Moxifloxacin are effective against legionnaires’ disease and many other types of pneumonia. If his fever has resolved and he is well, his pneumonia may have been cured. If he contracted Legionnaires’ disease, he may have gained some immunity since recurrent cases of Legionnaires’ disease is unusual. The chest x-ray may still show spots in the lung, but they will resolve over time. The important prognostic sign is resolution of fever and return of appetite. Your husband is likely cured with the antibiotics.


Clarithromycin efficacy against Legionella?

Can the Legionella bacterium survive in the lung even after a three week course of Clarithromycin (500mg) taken twice daily, and can it then re-infect the patient about two months later?

It is unlikely that Legionella could survive 3 weeks of clarithromycin if you responded within the first 5 days. Was the Legionnaires’ disease confirmed by a Legionella test ordered by a physician? If so, what is the name of the test?

Re-infection by Legionella is theoretically possible, but we have only seen one convincing case.


Here’s the timeline of my Legionella infection and my patient history. I’m a 60 yr old male recently retired carpenter, so I am fairly fit. There was an outbreak of Legionnaires’ here in Edinburgh Scotland, UK, in May 2012 which took three lives and hospitalized ~50.

I first had symptoms on May 5th which I thought was the flu. It rapidly progressed into high fever with vomiting and diarrhea. After three days, I was too wiped out and confused to seek medical help so I tried to battle through it.

On June 7, I was well enough to visit my doctor who sent me to the hospital where a blood sample was tested. I also had a chest x-ray. The blood sample was positive for Legionella, and I was given Clarithromycin (500mg).

About two weeks of being off my antibiotics, I began having symptoms of Legionnaires’. I had lower leg pain, headaches, a bit of diarrhea, and was coughing up phlegm. This only lasted a couple of days and I got back to normal.

A week later I gave a blood sample for my Legionella follow-up survey. My doctor called to say the sample was positive for Legionella and put me on a seven day course of Clarithromycin (500mg) again. I went for a chest x-ray where it was confirmed I had an infection of the lower lung. This is why I asked if it was possible to carry the Legionella bacteria after antibiotic treatment. I’m due to give another blood sample and I will await the results with interest.


The more important test is comparison of your next chest X-ray with the chest X-ray of 20/07/12. Your next chest X-ray may be abnormal for the next 2 – 3 months, but it should not be worse. If your fever has subsided, you are probably recovering.

Your Legionella blood test may remain abnormal for many more months, but that is not of concern – this test shows you contracted Legionnaires’ disease, but it is not that useful for measuring outcome.

Although the NHS maintains that cooling towers are a primary source, the actual source is the drinking water, and for reasons unclear, UK health officials rarely will admit to this likely possibility and therefore classify the source as unknown.

The following articles may be of interest to your physicians and can be downloaded from the Publications section.

Cooling towers and Legionellosis: A conundrum with proposed solutions

Legionnaires’ disease Contracted from Patient Homes: The Coming of the Third Plague?

Serology blood test for Legionella?

If a patient had been diagnosed with pneumonia in May can there be a test now (September) to see if they had had Legionnaires’?

The blood serology test for antibodies to Legionella may be positive for many years after contracting Legionnaire’s disease. A positive test at a high antibody titer is circumstantial evidence for Legionnaires’ disease. Unfortunately, a negative test is not helpful, i.e. if the test shows a low titer, this result does not rule out Legionnaires’ disease. You may need a medical authority to assist you with interpretation of this test.

Brain infection from Legionella?

Where exactly does Legionella travel in the body? Can it travel to the brain and through the blood after infection the lungs?

Legionella infects the lungs (pneumonia). It can travel by blood to other parts of the body including heart and kidney. Brain infection is extremely rare, but is theoretically possible.

Neurologic and central nervous system (brain, CNS) problems may also be due to immune-reactions to Legionella. See Lin COID 2011, page 351, top right.

Legionella urine antigen in an afebrile patient?

A hospitalized patient who was admitted with lung cancer (not on chemo) developed new wheezing and a shortness of breath, but does not have a fever. It has been seven days since their admission. The chest x-ray showed new small pleural effusions but no infiltrates. The urine antigen was positive, and there was no sputum produced. Another urine antigen was done five days later, but it showed up negative.

Could this still be possible hospital acquired Legionella despite the absence of fever (but new clinical respiratory findings) and a repeated urine antibody which was negative? I know the urine antigen can remain positive for weeks, but I did not know about a positive that can become a negative so soon.


The scenario you describe is somewhat unusual, as you indicate. The urine antigen will usually remain positive, even after receiving antibiotic therapy. But, on occasion the second one may be negative for a variety of reasons. One of them is that the pathogen may not be L. pneumophila serogroup 1, but another species or serogroup, and weak cross-reactivity with urinary antigen has occurred.

If you have pleural fluid available, the urinary antigen test may be positive in the pleural fluid. I would also obtain a third urinary antigen for confirmation.

At this point, obtain sera immediately and repeat it as an outpatient. Order antibody titers for Legionella pneumophila serogroups 1-6. The maximal time for seroconversion is three months. So, obtain sera acutely (best time is admission), about 4-6 weeks later, and again 3 months later. This may give you the answer if seroconversion is seen.


What is the best treatment for an ICU patient?

There is a patient in the ICU that has been diagnosed with Legionnaires’ disease. She was diagnosed with a positive Legionella serology test.


She has had a masectomy on one breast. She has a pacemaker. She also has had chronic spinal issues and walks with the aid of a walker.


What is the correct treatment for a patient who requires such intensive care? She is in the ICU and has been on a ventilator for about five days now. Her vital signs are looking pretty good and her heart is strong, but she is not getting better.

The drugs of choice for Legionnaires’ disease are:

Quiniolones: levofloxacin, moxifloxican

Macrolides: azithromycin, clarithromycin

Most patients who receive correct treatment early respond within five days (fever will disappear).  If she is receiving one of these antibiotics, she is being treated correctly. If an infection disease specialist is a consultant, I would guess that everything is being done for her and her care is appropriate.

Regardless, ICU physicians are well trained and knowledgeable about Legionnaires’ disease. The biggest problems in patients with Legionnaires’ disease is that disease is often overlooked by physicians. Your physicians have already made a correct diagnosis.

If she is deteriorating, we may recommend the addition of rifampin (600 mg/day) for only 3-5 days. This does not need to be done if an improvement is seen. Good luck.


Epidemiological link by urine antigen?

Legionella pneumonia is increasingly diagnosed only with urinary antigen rather than cultures, which are often no longer obtained in most hospitals. If UA is positive, how does one then link to enviroinmental samples?

As you know, the urinary antigen detects only L. pneumophila, serogroup 1.

If the Legionella in the environmental water sample is also L. pneumophila, serogroup 1, it is weak circumstantial evidence that the water may be the source. In essence, a positive match might be less useful than a negative match; a negative match might rule out the water as the source. This assumes that the water sample is performed as rigorously as our Special Pathogens Lab which uses multiple selective media and heat/acid treament to exclude contaminating flora.